Palatability and "mouth feel" are extremely important factors in formulating chewable tablets, especially pharmaceutical dosage forms. Many pharmaceutical and confectionery tablets are designed to be chewed either to provide proper flavorants or to increase the surface area of a particular drug to permit rapid activity in the digestive or circulatory system. Consequently, tablet formulations must be developed which will satisfy certain basic requirements:
sufficient cohesive properties to form a firm tablet under compression PA0 sufficient lubrication to prevent binding in the die cavities PA0 adequate flow to provide uniform weight PA0 absence of sticking under compression PA0 uniform drug dose and release after ingestion
production capability on high speed equipment
Furthermore, many pharmaceutical ingredients usually have both an unpleasant mouth feel and unpalatable taste due to chalkiness, grittiness, dryness and astringent properties of these materials. Accordingly, the practical value of these materials is substantially diminished since patients finding them objectionable may fail to take them as prescribed.
In an effort to overcome the above problems, flavorings have been employed with pharmaceuticals and especially antacids and vitamins to either mask or override the unpleasant dryness and astringent properties and chalkiness associated therewith. Unfortunately, it has been found that the flavoring merely masks the unpleasant taste, but the chalkiness, grittiness, dryness and astringent properties still remain.
U.S. Pat. No. 3,843,778 to Diamond et al. discloses a technique for coating antacid particles with a water insoluble, inert, non-toxic hydrocarbon oil which is formulated into suspensions or tablets which are said to be substantially free of the impalatable "mouth feel" properties associated with antacids. An electronegative agent, such as a surfactant selected from an alkyl aryl sulfonate, or an alkyl sulfate or sulfonate, or sulfonated amides or amines, or sulfated or sulfonated esters or ethers, or a dioctyl sulfosuccinate, or a hydrated aluminum silicate, such as bentonite or kaolin, is employed to aid in adhering the oil to the electropositively charged antacid particles.
U.S. Pat. No. 3,253,988 to Scott discloses an orally administrable antacid formed of oils or fats, that is, esters of higher fat acids and a trihydric alcohol, in combination with antacids. The Scott antacid may be in the form of a waxy solid, an emulsion or suspension.
U.S. Pat. No. 4,230,693 assigned to Armour-Dial, Inc. describes an antacid tablet containing fat, antacid, sugar, starch and water. It is prepared through a wet granulation technique and utilizes fats with melting points above body temperature. Also, the tablet press employed must be heated to 105.degree.-120.degree. F. to avoid sticking and adherence to punch faces. The antacid tablet is said to be prepared by mixing the antacid ingredient, water, sugar and fat to provide a powdered mixture, forming the mixture into a tablet shape and applying a pressure of from 50 to 600 psi to the mixture, the tabletting machine, including the punch elements of the presses, preferably being maintained at an elevated temperature.
The tablet may also be prepared by mixing the fat in liquid form and the antacid with the sugar and water, cooling the resultant mixture to a temperature of below 40.degree. F. and then passing the mixture through a mill to obtain a powdered mixture which is then formed into tablets.
Generally, tablets are normally made by direct compression wherein a mixture of tabletting compounds including active ingredient, flavor, bonders, etc., are fed to a die chamber of a tablet press and a tablet is formed by direct compaction. Hardness of the resulting tablet is a direct function of the compression pressure employed. Where it has been desired to produce a so-called "soft" tablet, that is, one which has easy bite-through, a disintegrator, such as alginic acid, is added to the pre-tablet mix. Alternatively, a soft tablet has been formed by employing reduced compression temperatures. The result in each instance has been essentially the same, namely, production of a softer tablet which is very fragile and brittle and is easily chipped.
It has also been suggested to employ a fatty material in the pre-tablet mix to attain tablet softness. However, it has been found that the addition of fats or oils to the pre-tablet mix causes tabletting ingredients to adhere to the die chamber and significant reduction in the bonding action of the bonders present in the mix.